thought exercise

[berdes]

Recently moved to the Coosa River in Alabama. Turns out there are a lot of shallows in this area, so the idea of a direct drive 40's style "gentleman's racer" style boat may not be feasible. Rather than switching to an outdrive, I was thinking of a jet. I don't see any major obstacles to doing that. Looking for opinions on such a swap and also any possible source for a drive or maybe a complete neglected jet boat with a usable drive to pirate from.

[engineermike]

How much power are you looking for?

[David]

I don’t think the big jet rooster tail would be appropriate for a gentlenan’s racer. An aluminum river racer jet boat would be fun. A gentleman’s racer is one of the coolest things in the water. The mix does not appeal to me.

More power to you though. What about a PWC power unit and jet?

[Bodhi]

Berdes, that swap will result in a significant loss of power. Jets are extremely inefficient with a bit more than 20% loss from the hp

[engineermike]

What about a PWC power unit and jet?

This is what I was thinking. The modern 4-stroke PWC power units are extremely simple, light-weight, reliable, and powerful. No gears or water pump to fail either, and the steering is very simple with low effort and no maintenance.


Berdes, that swap will result in a significant loss of power. Jets are extremely inefficient with a bit more than 20% loss from the hp

True as well. Years ago, somebody converted a Yamaha GP1300R, a 160 hp ski, from a jet drive to a propeller. It went from 65 mph to over 90 on the same power level. However, it had a nasty habit of making 90 deg turns at high speeds with no notice.

[Bodhi]

I've heard a rumor that those types of turns should be avoided ...ha

[berdes]

Good points all. Didn't know there was a four cycle PWC so I'll have to look into that. I don't think the two cycles would cut it for several reasons, including the lack of the V8 rumble.
Most of the racers had four or six bangers in them, so any modern V8 should have plenty of power even at 20% loss to move it along well enough? Cool factor is the secondary motivator here so might even get the leather helmet and steam punk goggles.

[engineermike]

The 4-cycle pwcs are over 300 hp now but the biggest ones are just 4-bangers

[Bodhi]

As you mention v8 power, the wheels started turning and I am imagining a v8 rude motor hooked up to the pump.....plenty of power...and it'll still smoke!

[berdes]

As happens so often, at least to me, life made a 90 deg. turn and I found and bought this:487266
It's a 17' Alsberg based on a '39 Century Thunderbolt racer with a 175 hp Mercury jet in it. Best top end almost 55, and good fuel economy too. Front hatch opens to seat two additional passengers. Nice find, no?
The picture with the duelly trailer is, I think, an original. The one on the single axel trailer is the Alsberg.

[rock]

very nice

[David]

Custom build?

[berdes]

Custom build?

No. Alsberg was a builder with a projected output of 100 units per year. They were only in business for a year, and by some reports only produced 30 copies of this boat.